KR102589611B1 - Systems and methods for methodologies with layer-specific illumination spectra - Google Patents

Abstract

The metrology system includes an image device and a controller. The imaging device includes a spectrally tunable illumination device and a spectrally tunable illumination device for generating an image of a sample having metrology target elements on two or more sample layers based on radiation emitted from the sample in response to illumination from the spectrally tunable illumination device. Includes a detector for The controller determines layer-specific imaging configurations of imaging devices for imaging metrology target elements on two or more sample layers within selected image quality tolerances, each layer-specific imaging configuration being selected from a spectrally tunable illumination device. Includes the lighting spectrum. The controller additionally receives one or more images of the metrology target element on two or more sample layers generated using layer-specific imaging configurations. The controller also provides metrology measurements based on one or more images of metrology target elements on two or more sample layers.

Description

Systems and methods for methodologies with layer-specific illumination spectra

<Cross-reference to related applications>

This application was filed on April 5, 2017, with Amnon Manassen, Daria Negri, Andrew Hill, Ohad Bachar, Vladimir Levinski, and Yuri Paskover as inventors, and the title of the invention is OVERLAY METROLOGY WITH PROCESS LAYERS ILLUMINATED BY DIFFERENT SPECTRA 35 U.S.C. in U.S. Provisional Application Serial No. 62/481,685. §119(e), the provisional application being hereby incorporated by reference in its entirety.

<Technology field>

This disclosure relates generally to metrology systems, and more specifically to multi-layer metrology with layer-specific configuration.

Metrology systems suitable for characterizing multi-layer samples, such as semiconductor devices, may analyze any number of layers on the sample. However, the metrology measurements of any given layer may be affected by the surrounding material, and as a result, a given configuration of the metrology system will not perform to the same extent (e.g., precision, repeatability, etc.) for all sample layers. may not be provided. For example, metrology of a subsurface layer may involve propagating an illumination beam through one or more transparent or translucent layers near the surface and receiving radiation from the subsurface layer through the transparent or translucent layer. It may be possible. Accordingly, metrology performance may be highly layer-specific, and certain aspects of the sample layout, such as, but not limited to, the thickness of the sample layer, the optical properties of the sample layer, or patterned features on the sample layer. It may depend on . Accordingly, it would be desirable to provide a system and method for remedying deficiencies such as those identified above.

A metrology system in accordance with one or more example embodiments of the present disclosure is disclosed. In one example embodiment, the system includes an imaging device. In another example embodiment, the imaging device includes a spectrally tunable lighting device. In another example embodiment, an imaging device is configured to generate an image of a sample comprising metrology target elements on two or more sample layers based on radiation emitted from the sample in response to illumination from a spectrally tunable illumination device. Includes a detector for In another example embodiment, the system includes a controller communicatively coupled to the imaging device. In another example embodiment, the controller determines a layer-specific imaging configuration of the imaging device for imaging metrology target elements on two or more sample layers within selected image quality tolerances, wherein each layer-specific imaging configuration The configuration includes an illumination spectrum from a spectrally tunable illumination device. In another example embodiment, the controller receives from an imaging device one or more images of metrology target elements on two or more sample layers generated using layer-specific imaging configurations. In another example embodiment, the controller provides metrology measurements based on one or more images of metrology target elements on two or more sample layers.

A metrology system in accordance with one or more example embodiments of the present disclosure is disclosed. In one example embodiment, the system includes an imaging device. In another example embodiment, the imaging device includes a broadband illumination device. In another example embodiment, the imaging device includes a spectrally tunable filter to spectrally filter radiation emitted from the sample in response to illumination from a broadband illumination device. In another example embodiment, the imaging device includes a detector for generating an image of a sample comprising two or more sample layers based on radiation emitted from the sample and filtered by a spectrally tunable filter. In another example embodiment, the system includes a controller communicatively coupled to the imaging device. In another example embodiment, the controller determines layer-specific imaging configurations of an imaging device for imaging metrology target elements on two or more sample layers within selected image quality tolerances, wherein each layer-specific imaging configuration is spectrally contains the spectrum of radiation from the sample filtered by a tunable filter. In another example embodiment, the controller receives from the detector one or more images of metrology target elements on two or more sample layers generated using layer-specific imaging configurations. In another example embodiment, the controller provides metrology measurements based on one or more images of metrology target elements on two or more sample layers.

A method in accordance with one or more example embodiments of the present disclosure is disclosed. In one example embodiment, the method includes determining layer-specific imaging configurations of an imaging device for imaging metrology target elements on two or more sample layers of a sample within selected image quality tolerances, wherein each layer The unique imaging configuration includes an imaging spectrum. In another example embodiment, the method includes receiving from an imaging device one or more images of metrology target elements on two or more sample layers generated using a layer-specific imaging configuration. In another example embodiment, the method includes providing metrology measurements based on one or more images of metrology target elements on two or more sample layers.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not necessarily limiting of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the general description, serve to explain the principles of the present invention.

The various advantages of the present disclosure may be better understood by those skilled in the art by reference to the accompanying drawings, in which:
1 is a conceptual diagram illustrating an imaging device, according to one or more embodiments of the present disclosure.
2A is a conceptual diagram of a spectrally tunable illumination source, according to one or more embodiments of the present disclosure.
FIG. 2B is a conceptual diagram of an illumination source including a broadband source and a double monochromator for selectively filtering the spectrum of the broadband source, according to one or more embodiments of the present disclosure.
FIG. 2C is a conceptual diagram of a multi-channel illumination source including a broadband source and multiple filtering channels with fixed spectral transmittance, according to one or more embodiments of the present disclosure.
3 is a conceptual diagram of an imaging device, according to one or more embodiments of the present disclosure.
4 is a flow diagram illustrating steps performed in a method for image-based metrology with layer-specific imaging configurations, according to one or more embodiments of the present disclosure.

Detailed reference will now be made to the disclosed subject matter, which is illustrated in the accompanying drawings. The present disclosure is particularly shown and described with respect to certain embodiments and specific features of certain embodiments. The embodiments described herein are to be considered illustrative rather than limiting. It should be readily apparent to those skilled in the art that various changes and modifications may be made in form and detail without departing from the spirit and scope of the present disclosure.

Embodiments of the present disclosure relate to systems and methods for imaging multiple layers of a sample using layer-specific imaging configurations. For example, the imaging configuration may include the spectrum of illumination incident on the sample to be imaged, the illumination profile, the spectrum of radiation incident on the detector, the position of the sample within the focal volume (e.g., focus position), and the field stop. ), the configuration of the aperture stop (e.g., to modify image and/or object-space telecentricity, or the like), or the detector parameters (e.g., gain, integration time, etc.), but is not limited to these. Accordingly, embodiments of the present disclosure relate to creating tailored imaging configurations for accurate imaging of features located on different layers of interest on a sample.

It is recognized herein that an imaging system may generate an image of a sample layer by illuminating the sample and detecting radiation emitted from the sample in response to the illumination. In a general sense, radiation may be emitted from any layer of the sample in response to incident illumination through a wide range of interaction mechanisms, including but not limited to reflection, scattering, diffraction, or luminescence. Additionally, the imaging system may produce a focused image of a feature within a depth of field defined at least in part by the spectrum of illumination and the numerical aperture (NA) of the system. . Accordingly, the imaging system may be configured to image sub-surface features of a translucent sample within a depth of field as well as features on the surface of the sample.

Subsurface layers may be imaged by propagating illumination through any near-surface layer and detecting radiation based on its interaction with the subsurface layer of interest. Radiation emitted from the subsurface layer of interest may propagate further through the near-surface layer to reach the detector. The resulting imaging signal associated with the sub-surface layer may therefore be influenced by the near-surface layer. For example, a near-surface layer may absorb light of certain wavelengths. Additionally, near-surface layers may refract light at any interface between layers or between different materials on a single layer, which may modify the focusing of the light and/or create a wavelength-dependent optical path through the sample. Dispersion (e.g., chromatic aberration) may be introduced. Patterned features on any sample layer may further affect the resulting imaging signal through scattering and/or diffraction.

Accordingly, it may be the case that image quality may vary for features on different sample layers when imaged using a single imaging configuration due to differences in the optical path between the sample layers. Image quality may be measured according to any metric such as, but not limited to, image contrast, image brightness, or image noise. Moreover, even if the imaging configuration is tailored to provide images of two or more sample layers (e.g., by generating customized illumination spectra, etc.), the customized imaging configuration may be tailored to provide images of one or more image quality metrics. There may be instances where it may not be possible to provide images of each layer of interest within desired tolerances. Additional embodiments of the present disclosure relate to creating customized layer-specific imaging configurations for multiple sample layers of interest to provide images of features on each sample layer of interest within selected image quality tolerances.

It is also recognized herein that the precision and/or repeatability of metrology measurements based on images of different layers of a sample may vary based on image quality. For example, the spectral content of the illumination may affect the perceived location of a feature differently for different sample layers. Such variations in the recognized positions of features in the image of a sample layer may be particularly problematic in overlay metrology, where the relative positions of features on multiple layers are utilized to determine overlay error.

Additional embodiments relate to performing metrology measurements on two or more layers of a sample using layer-specific imaging configurations. Additionally, layer-specific imaging configurations may be used with any metrology system known in the art to provide metrology performance within selected tolerances. For example, image-based overlay metrology involves imaging overlay target features on two or more layers of interest using customized layer-specific measurement conditions and determining the overlay error of the layers based on the layer-specific images. It can also be performed by In this regard, the overlay target features on each layer may be imaged using a layer-specific imaging configuration that is tailored based on the specific sample to provide images with image quality metrics within selected tolerances. As another example, the metrology system may use a layer-specific imaging configuration to measure one or more aspects of patterned features on a sample layer (eg, critical dimension, sidewall angle, or the like).

Metrology measurements on two or more layers, produced using layer-specific imaging configurations, may be performed sequentially or simultaneously. For example, a metrology measurement may be performed on a first layer of interest using a first set of metrology conditions, and subsequently a metrology measurement may be performed on a second layer of interest using a second set of metrology conditions. It may be carried out, and so on. As another example, metrology measurements of spatially separated features on different sample layers may be performed simultaneously using layer-specific metrology configurations. For example, spatially separated features on different sample layers (e.g., features of an overlay metrology target located on multiple sample layers) can be imaged on a detector with a selected image quality tolerance for features in all layers of interest. Different layers may be illuminated simultaneously using their own illumination spectra to provide a single image.

Additional embodiments relate to determining layer-specific metrology configurations for two or more layers of a sample. For example, a layer-specific metrology configuration may be determined by simulating the metrology of each sample layer of interest based on a three-dimensional representation of the multi-layer sample. As another example, a layer-specific metrology configuration may be determined experimentally based on a series of metrology measurements for each sample layer of interest using various metrology conditions. Additional embodiments relate to providing metrology measurements with layer-specific metrology configurations for two or more layers of a sample.

A further embodiment relates to a metrology system suitable for providing layer-specific metrology on a multi-layer sample. For example, a metrology system suitable to provide layer-specific metrology measurements may include, for example, a spectrally tunable illumination device to generate a layer-specific illumination spectrum, a spectrally tunable filter, and a translational device to provide layer-specific sample positions. A configurable sample stage, a configurable field of view aperture, a configurable aperture aperture (e.g., to adjust image and/or object-space telecentricity), or configurable parameters (e.g., gain, integration time, or etc.), but it is not necessary to include them.

1 is a conceptual diagram illustrating an imaging device 100, according to one or more embodiments of the present disclosure. Additionally, imaging device 100 may include a metrology device for determining one or more metrology measurements based on images generated by imaging device 100. In this regard, imaging device 100 may measure alignment using any method known in the art. In one embodiment, imaging device 100 includes an image-based metrology tool for performing metrology measurements (e.g., overlay measurements, feature size measurements, etc.) based on one or more images of the sample layer. do. In another embodiment, imaging device 100 includes a scatterometry-based metrology tool for performing metrology measurements based on scattering (reflection, diffraction, diffuse scattering, or the like) of light from the sample.

In one embodiment, imaging device 100 includes an illumination source 102 for generating an illumination beam 104. The illumination beam 104 includes vacuum ultraviolet radiation (VUV), deep ultraviolet radiation (DUV), ultraviolet (UV) radiation, visible radiation, or infrared (IR) radiation. However, it may also include, but is not limited to, light of one or more selected wavelengths. Illumination source 102 may further produce an illumination beam 104 comprising a random range of selected wavelengths. In another embodiment, illumination source 102 may include a spectrally tunable illumination source to generate illumination beam 104 with a tunable spectrum.

Illumination source 102 may further produce an illumination beam 104 with an arbitrary temporal profile. For example, the illumination beam 104 produced by the illumination source 102 may include a continuous profile, a pulsed profile, or a modulated profile. Additionally, the illumination beam 104 may be delivered from the illumination source 102 via free space propagation or guided light (eg, optical fiber, light pipe, or the like).

In another embodiment, illumination source 102 directs an illumination beam 104 to sample 106 through an illumination pathway 108. In another embodiment, imaging device 100 includes an objective lens 114 for focusing the illumination beam 104 onto the sample 106.

Illumination passageway 108 may include one or more lenses 110 or additional optical components 112 suitable for modifying and/or conditioning the illumination beam 104. For example, one or more optical components 112 may include one or more polarizers, one or more filters, one or more beam splitters, one or more diffusers, one or more homogenizers, and one or more apodizers. It may include, but is not limited to, an apodizer, or one or more beam shapers. As another example, one or more optical components 112 include an aperture stop to control the angle of illumination to sample 106 and/or a field of view stop to control the spatial extent of illumination to sample 106. You may. In one instance, illumination path 108 includes an aperture stop positioned in a plane conjugate to the rear focal plane of objective lens 114 to provide telecentric illumination of the sample. In another embodiment, sample 106 is placed on sample stage 116. Sample stage 116 may include any device suitable for positioning sample 106 within imaging device 100. For example, sample stage 116 may include any combination of a linear translation stage, a rotation stage, a tip/tilt stage, or the like.

In another embodiment, imaging device 100 includes a detector 118 configured to capture radiation emitted from sample 106 through collection passage 120. For example, collection passageway 120 may include a collection lens (e.g., objective lens 114 as illustrated in Figure 1) or one or more additional collection passageway lenses 122, but they do not necessarily There is no need to include it. As another example, detector 118 may receive reflected or scattered radiation from sample 106 (eg, via specular reflection, diffuse reflection, and the like). As another example, detector 118 may receive radiation produced by sample 106 (e.g., luminescence associated with absorption of illumination beam 104, or the like).

Detector 118 may include any type of optical detector known in the art suitable for measuring illumination received from sample 106. For example, detector 118 may include, but is not limited to, a CCD detector, a TDI detector, a photomultiplier tube (PMT), an avalanche photodiode (APD), or the like. does not In other embodiments, detector 118 may include a spectroscopic detector suitable for identifying the wavelength of radiation emitted from sample 106. In another embodiment, imaging device 100 includes multiple detectors (e.g., associated with multiple beam paths generated by one or more beamsplitters to facilitate multiple metrology measurements by imaging device 100). It may also include (118).

Collection passage 120 is configured to collect illumination by objective lens 114, including but not limited to one or more collection passage lenses 122, one or more filters, one or more polarizers, or one or more beam blocks. It may further include any number of optical elements for directing and/or modifying. Additionally, collection passage 120 may be configured to control the field of view aperture for controlling the spatial extent of the sample imaged onto detector 118 or the angular extent of illumination from the sample used to generate an image on detector 118. It may also include an aperture aperture for In another embodiment, collection passage 120 includes an aperture stop located in a plane conjugate to the rear focal plane of the optical element of objective lens 114 to provide telecentric imaging of the sample.

In one embodiment, as illustrated in FIG. 1 , imaging device 100 may have objective lens 114 simultaneously direct illumination beam 104 to sample 106 and emit light from sample 106 . It includes a beam splitter 124 that is oriented to collect radiation. In this regard, imaging device 100 may be configured in epi-illumination mode.

In other embodiments, the angle of incidence of the illumination beam 104 relative to the sample 106 is adjustable. For example, the path of illumination beam 104 through beamsplitter 124 and objective lens 114 may be adjusted to control the angle of incidence of illumination beam 104 with respect to sample 106. In this regard, illumination beam 104 follows a nominal path through beamsplitter 124 and objective lens 114 such that illumination beam 104 has a normal angle of incidence with respect to sample 106. You can have it. As another example, the angle of incidence of the illumination beam 104 with respect to the sample 106 can be adjusted (e.g., by a rotatable mirror, spatial light modulator, freeform illumination source, etc.) to adjust the illumination beam to the beamsplitter 124. It may also be controlled by modifying the position and/or angle of 104. In another embodiment, illumination source 102 directs one or more illumination beams 104 at an angle (e.g., glancing angle, 45 degree angle, or the like) at sample 106.

In another embodiment, imaging device 100 includes controller 126. In another embodiment, controller 126 includes one or more processors 128 configured to execute program instructions maintained on memory medium 130. In this regard, one or more processors 128 of controller 126 may execute any of the various process steps described throughout this disclosure. Additionally, the controller 126 may provide metrology data (e.g., alignment measurement results, images of targets, pupil images, and the like) or metrology metrics (e.g., precision, tool induced shift, sensitivity, diffraction efficiency, etc.). , and etc.) may be configured to receive data including, but not limited to.

One or more processors 128 of controller 126 may include any processing elements known in the art. In this sense, one or more processors 128 may include any microprocessor type device configured to execute algorithms and/or instructions. In one embodiment, one or more processors 128 are configured to execute a program configured to operate imaging device 100, as described throughout this disclosure, such as a desktop computer, a mainframe computer system, or It may consist of a workstation, an imaging computer, a parallel processor, or any other computer system (e.g., a networked computer). It is also recognized that the term “processor” may be defined broadly to encompass any device having one or more processing elements that execute program instructions from non-transitory memory medium 130. Additionally, the steps described throughout this disclosure may be performed by a single controller 126, or alternatively, by multiple controllers 126. Additionally, controller 126 may include one or more controllers housed within a common housing or within multiple housings. In this way, any controller or combination of controllers may be individually packaged as a module suitable for integration into imaging device 100. Additionally, controller 126 may analyze data received from detector 118 and provide that data to additional components within imaging device 100 or external to imaging device 100.

Memory medium 130 may include any storage medium known in the art suitable for storing program instructions executable by an associated one or more processors 128. For example, memory medium 130 may include a non-transitory memory medium. As another example, memory media 130 may include, but is not limited to, read only memory, random access memory, magnetic or optical memory devices (e.g., disks), magnetic tape, solid state drives, and the like. It doesn't work. It is also noted that memory medium 130 may be housed in a common controller housing with one or more processors 128. In one embodiment, memory medium 130 may be located remotely relative to the physical location of one or more processors 128 and controller 126. For example, one or more processors 128 of controller 126 may access remote memory (e.g., a server) accessible via a network (e.g., Internet, intranet, etc.). Accordingly, the above-mentioned description should not be construed as a limitation on the present invention, but rather as an example only.

In another embodiment, controller 126 is communicatively coupled to one or more elements of imaging device 100 to provide layer-specific metrology configuration information. For example, the controller 126 may manipulate the illumination beam 104 and/or radiation from the sample captured by the detector 118 at the illumination source 102 to control the spectrum of illumination incident on the sample. may be communicatively coupled to one or more apertures to , but not necessarily coupled.

In one embodiment, the layer-specific imaging configuration includes a layer-specific spectrum of illumination incident on sample 106. Accordingly, illumination source 102 may be configured as a spectrally tunable illumination source to provide a layer-specific illumination spectrum for metrology. It is recognized herein that illumination source 102 may include a source of illumination and any number of additional components for conditioning illumination from the illumination source. Additionally, additional components may share a common container with illumination source 102 or may be integrated into imaging device 100.

2A-2C illustrate a spectrally tunable illumination source, according to an embodiment of the present disclosure.

FIG. 2A is a conceptual diagram of a spectrally tunable illumination source 102, according to one or more embodiments of the present disclosure. In one embodiment, the illumination source 102 is a broadband source 202 that has a broad spectrum (e.g., a range of wavelengths of illumination) and filters the spectrum of the broadband source 202 to create a layer-specific illumination spectrum. It includes a tunable spectral filter 204 for: In another embodiment, illumination source 102 includes a neutral density filter 206 (e.g., a wavelength independent filter) to adjust the power of illumination beam 104. Neutral density filter 206 may be a polarization rotator coupled to a polarizer, one or more filters with a fixed optical density, or a gradient filter with an optical density that varies as a function of position across the filter. It may also include any type of wavelength independent filter known in the art, such as, but not limited to, these. Additionally, neutral density filter 206 may include a filter control device 208 to selectively modify the transmission of neutral density filter 206. For example, the filter control device 208 may include an adjustable polarization rotator for selectively adjusting the polarization of the illumination beam 104 ahead of the polarizer (e.g., as illustrated in FIG. 2A ). 104) includes a filter wheel for selectively placing one of several filters in the path, or a translation device (e.g., a rotation device, a linear translation device, or the like) for selectively placing a gradient filter. You may, but are not limited to these.

Broadband source 202 may include any source of illumination suitable to provide an illumination beam 104 with a range of wavelengths for metrology. In one embodiment, broadband source 202 is a laser source. For example, broadband source 202 may include, but is not limited to, a broadband laser source, a supercontinuum laser source, a white light laser source, or the like. In this regard, the broadband source 202 may provide an illumination beam 104 with high coherence (eg, high spatial coherence and/or temporal coherence). In another embodiment, broadband source 202 includes a laser-sustained plasma (LSP) source. For example, the broadband source 202 may include an LSP lamp, an LSP bulb, or an LSP chamber suitable for containing one or more elements that may emit broadband illumination when excited into a plasma state by a laser source. , but is not limited to these. In another embodiment, broadband source 202 includes a lamp source. For example, broadband source 202 may include, but is not limited to, an arc lamp, a discharge lamp, an electrodeless lamp, or the like. In this regard, the broadband source 202 may provide an illumination beam 104 with low coherence (eg, low spatial coherence and/or temporal coherence).

Tunable spectral filter 204 may modify the spectrum of incident illumination (e.g., illumination beam 104 produced by broadband source 202) by reducing the spectral power of selected wavelengths relative to others. there is. Accordingly, the spectral transmittance of a spectral filter may describe the transmittance of illumination as a function of wavelength (e.g., 0% to 100%, 0 to 1, etc.). Note that transmittance may refer to the light that passes by a filter through transmission and/or reflection. A typical spectral filter may, but need not, include one or more spatial filters or one or more wavelength-dependent filters located in the lens Fourier plane where the spectral content is spatially distributed. Additionally, tunable spectral filter 204 may modify the spectral transmittance according to an arbitrary distribution. For example, the tunable spectral filter 204 may include a low-pass filter to attenuate wavelengths above the cutoff wavelength, a high-pass filter to attenuate wavelengths below the cutoff wavelength, A band-pass filter to pass a defined spectral bandwidth of the light and attenuate wavelengths outside a selected band of wavelengths, and a band-reject filter to attenuate wavelengths within a selected band of wavelengths. , filters with tailored spectral transmittance distributions, or the like.

Tunable spectral filter 204 may include any type of device suitable for filtering the spectrum of broadband source 202. In one embodiment, tunable spectral filter 204 includes one or more filters with tunable spectral transmission. In this regard, the spectral transmission of the tunable filter in the path of the illumination beam 104 may be selectively modified to provide a layer-specific illumination spectrum. For example, tunable spectral filter 204 may, but need not, include a thin film tunable filter formed from one or more stacked layers of dielectric material. Additionally, tunable spectral filter 204 may include a reflective spectral filter or a transmissive spectral filter. Additionally, spectral filters may be formed from a single optical element or a combination of optical elements.

In another embodiment, tunable spectral filter 204 includes one or more components with orientation dependent spectral transmission. For example, as illustrated in FIG. 2A, tunable spectral filter 204 may include one or more edge filters (e.g., edge filters) with position sensing cutoff wavelengths that vary (e.g., linearly) across the filter. It may also include a filter 204a and an edge filter 204b. Accordingly, a layer-specific illumination spectrum may be obtained by adjusting the position of edge filters 204a and 204b relative to the path of illumination beam 104 (e.g., via controller 126). As another example, the tunable spectral filter 204 may include an angularly tunable filter coupled to a rotation device to selectively modify the angle of incidence of the illumination beam 104 on the angularly tunable filter. .

In another embodiment, the tunable spectral filter 204 may include one or more filters having a fixed spectral transmittance and a filter insertion for selectively inserting a filter in the path of the illumination beam 104 to provide a layer-specific illumination spectrum. Includes devices. A filter insertion device may include any combination of elements suitable for selectively inserting a filter into the path of the illumination beam 104. For example, the filter insertion device may include components for selectively rotating one or more filters into the path of the illumination beam 104, such as, but not limited to, a filter wheel or flipper device. there is. As another example, a filter insertion device may linearly insert one or more filters into the path of the illumination beam 104, such as, but not limited to, a mount for securing one or more filters attached to a linearly translatable stage. It may also include components for translation.

In another embodiment, tunable spectral filter 204 includes at least one dispersive element coupled with a spatial filter to modify the spectrum of broadband source 202. FIG. 2B is a conceptual diagram of an illumination source 102 including a broadband source 202 and a double monochromator for selectively filtering the spectrum of the broadband source 202, according to one or more embodiments of the present disclosure. A system and method for spectral tuning of a broadband light source using a double monochromator is generally described in U.S. Patent Application No. 15/339,312, filed October 31, 2016, which patent application is incorporated by reference. The entirety is incorporated into this institution. In one embodiment, the tunable spectral filter 204 includes a first tunable dispersion element 210 for introducing spectral dispersion into the illumination from the broadband source 202, the spectral dispersion of the illumination from the broadband source 202. A first optical element 212 (e.g., one or more lens, or the like), a spatial filtering element 216 for filtering the illumination from a broadband source 202 based on the distribution of the spectrum in the focal plane, and spatially distributed illumination delivered by the spatial filtering element 216. a second optical element 218 (e.g., one or more lenses, etc.) for collecting, and removing the dispersion introduced by the first tunable dispersing element 210 to produce an illumination beam 104. It includes a second tunable dispersion element 220 for.

For example, the first tunable dispersive element 210 may be configured such that the spectrum of illumination from the broadband source 202 may be spatially distributed across the beam profile at the focal point of the first tunable dispersive element 210. Illumination from broadband source 202 may be spatially distributed. Spatial filtering element 216 may selectively pass or block a portion of the illumination from broadband source 202. In this regard, the spectral transmission of tunable spectral filter 204 may be related to the spatial transmission of spatial filtering element 216. For example, as illustrated in FIG. 2B, illumination from broadband source 202 may include three wavelength components (λ ₁ , λ ₂ and λ ₃ ), and spatial filtering element 216 may provide λ ₂ can be selectively passed to form a layer-specific lighting spectrum. Furthermore, the second tunable dispersive element 220 is introduced by the first tunable dispersive element 210 such that the spectrum of the illumination from the broadband source 202 is no longer spatially distributed across the beam profile. The spectral dispersion collected by the two optical elements 218 may be removed. For example, the dispersion of the second tunable dispersion element 220 can be dynamically adjusted to correspond to the dispersion of the first tunable dispersion element 210 to eliminate the dispersion introduced by the first tunable dispersion element 210. You may. Accordingly, tunable spectral filter 204 may filter the spectral content of illumination from broadband source 202 without modifying additional beam characteristics (eg, divergence angle, or the like).

Dispersing elements (e.g., first tunable dispersing element 210 or second tunable dispersing element 220) are known in the art suitable for introducing spectral dispersion into the illumination from broadband source 202. It may be any type of distributed element. For example, the dispersing element may modify the dispersion into the illumination from the broadband source 202 through any mechanism, such as diffraction or refraction. Additionally, the first tunable dispersing element 210 may be formed from transmissive and/or reflective optical elements. In one instance, the first tunable dispersing element 210 includes a dynamically generated diffraction grating (eg, an acousto-optic modulator, or the like). In this regard, the diffraction grating may be dynamically generated in a substrate material (eg, a transparent optical material). Additionally, the dispersion may be dynamically modified to tune the tunable spectral filter 204 by adjusting the physical properties of the dynamically generated diffraction grating. For example, the period or modulation depth of a dynamically generated diffraction grating may be adjusted (e.g., via controller 126) to control the value of dispersion (e.g., the angle at which a particular wavelength of illumination is diffracted). there is. As another example, the modulation depth of the dynamically generated diffraction grating may be adjusted (e.g., via controller 126) to control the efficiency of dispersion (e.g., the efficiency value at which a particular wavelength of illumination is diffracted). .

In another embodiment, lighting source 102 includes a multi-channel lighting source. A multi-channel illumination source for high-speed spectral selection is generally described in U.S. Patent Application No. 15/387,180, filed December 21, 2016, which is hereby incorporated by reference in its entirety. FIG. 2C is a conceptual diagram of a multi-channel illumination source including a broadband source 202 and multiple filtering channels with fixed spectral transmittance, according to one or more embodiments of the present disclosure. In one embodiment, the multi-channel illumination source includes a channel selector 222 to direct illumination from the broadband source 202 to two or more filtering channels 224, where each of the filtering channels 224 and filters 226 with different spectral transmittances. Additionally, the multi-channel illumination source may include a beam combiner 228 to combine illumination from any of the filtering channels 224 into an illumination beam 104. Accordingly, a multi-channel illumination source may adjust channel selector 222 (e.g., via controller 126) to direct illumination from broadband source 202 through one or more selected filtering channels 224. By doing so, it is possible to provide a layer-specific lighting spectrum.

Channel selector 222 may include any optical element or set of optical elements suitable for directing illumination from broadband source 202 into any combination of filtering channels 224 . For example, channel selector 222 may include one or more beamsplitters 230. As another example, channel selector 222 may include one or more dichroic mirrors. As a further example, as illustrated in FIG. 2C, channel selector 222 may include a polarization rotator 232 (e.g., a wave plate, electro-optical cell, or the like). there is. Additionally, channel selector 222 may include one or more polarized beamsplitters (e.g., beamsplitter 230, etc.). In this regard, the relative intensity of illumination in the filtering channel 224 may be controllable by adjusting the polarization rotator 232 with respect to the orientation of the polarized beam splitter. Additionally, channel selector 222 may include one or more shutters to control the distribution of illumination to filtering channels 224.

A multi-channel illumination source may provide one or more beams associated with a layer-specific illumination spectrum to be directed to the sample. In this regard, an imaging device 100 comprising a multi-channel illumination source with independent spectral control for each of the filtering channels 224 can be used to image a sample using a selectively controlled spectrum over a wide continuous range of wavelengths. It can also be illuminated. Additionally, a multi-channel illumination source may illuminate the sample simultaneously or sequentially using illumination from each channel. Additionally, a multi-channel illumination source may use different channels of illumination to illuminate different portions of the sample (eg, different cells of the metrology target, or etc.). In this regard, a multi-channel illumination source may provide different layer-specific illumination spectra to different regions of the sample (eg, features of a metrology target located on different layers, etc.).

In another embodiment (not shown), illumination source 102 includes multiple narrowband illumination sources and a source selector to provide a layer-specific illumination spectrum comprising any combination of illumination from narrowband illumination sources. Includes. For example, a narrowband illumination source may, but need not, include a laser source with different spectral characteristics. Additionally, the source selector may include any combination of elements suitable for selecting illumination from one or more narrowband illumination sources. For example, the source selector may include, but is not limited to, one or more beamsplitters, one or more shutters, one or more wave plates, one or more polarizers, one or more beam combiners, or one or more shutters.

In another embodiment, the layer-specific imaging configuration includes a layer-specific detection spectrum. For example, illumination source 102 may be configured with a fixed spectrum (e.g., a broadband spectrum) and imaging device 100 may be configured to have a sample (e.g., a broadband spectrum) used to generate an image on detector 118. 106) may further include a tunable spectral filter to match the spectrum of radiation emitted from the device. In one instance, imaging device 100 may include a tunable spectral filter ahead of the detector in collection passage 120 to provide a layer-specific detection spectrum. Tunable spectral filters may include any type of tunable filter, such as, but not limited to, a selectable set of filters with fixed spectral transmission, one or more filters with orientation dependent spectral transmission, or the like. It may be possible.

In another embodiment, although not shown, the collection passageway 120 of imaging device 100 includes two or more detectors 118 for simultaneous generation of images of the sample that are filtered according to the detection spectra unique to the two or more layers. ) includes. For example, the collection passage 120 may include one or more beam splitters to split radiation emitted from the sample into two or more detection channels. Each detection channel may further include a filter for providing a layer-specific detection spectrum and a detector 118 for generating an image of the sample using the layer-specific detection spectrum.

The layer-specific imaging configuration may include the location and/or opening diameter of one or more stops within the system to align the path of light within imaging device 100. 3 is a conceptual diagram of imaging device 100, according to one or more embodiments of the present disclosure. In one embodiment, imaging device 100 includes one or more aperture stops. In a general sense, the aperture stop may limit the angular range of light propagating through the system. For example, as illustrated in Figure 3, the aperture stop 302 in the illumination path 108 may provide a layer-specific angular range of illumination to the sample. By another example (not shown), the aperture stop in the collection passageway 120 may provide layer-specific limits on the angular range of radiation emitted from the sample used to generate the image.

In other embodiments, the layer-specific imaging configuration includes the opening diameter of the aperture stop in the illumination passageway 108 and/or the collection passageway 120. Accordingly, imaging device 100 may include an aperture stop with an adjustable opening diameter (e.g., coupled to controller 126) for creation of layer-specific imaging configurations.

In another embodiment, the layer-specific imaging configuration includes the location of the aperture stop in the illumination passageway 108 and/or the collection passageway 120. For example, an aperture stop (e.g., aperture stop 302) located in the plane conjugate of the focus point of objective lens 114 in illumination path 108 may provide telecentric illumination of sample 106. may also be provided. In this regard, the angular range of illumination on sample 106 may be limited to substantially parallel beams. As another example, an aperture stop positioned in the plane conjugate to the focus point of objective lens 114 in collection passage 120 may be configured to cause the observed size of the feature to be greater than that of objective lens 114 (e.g., sample 106). may provide telecentric imaging of the sample 106, such that it may depend on the distance from the layer of the sample 106.

Herein, the exact location of the focus point of objective lens 114 may vary depending on the wavelength (e.g., of the radiation emitted from sample 106 or It is recognized that it may vary based on the wavelength of the illumination spectrum. Accordingly, the layer-specific imaging configuration determines the exact location of the aperture stop in the illumination passageway 108 and/or collection passageway 120 to adjust the telecentricity of the imaging and/or illumination to be within selected tolerances. It may also be included. For example, imaging device 100 may be configured (e.g., coupled to controller 126) to position an aperture as an aperture stop within illumination passageway 108 and/or collection passageway 120. It may also include a positioning device 304. Positioning device 304 may be configured to provide an aperture stop (e.g., an aperture stop) in imaging device 100, such as, but not limited to, a linearly translatable stage, a rotationally translatable stage, or the like. (302)) may include any combination of elements suitable for placement.

Additionally, imaging device 100 may include any number of optical elements for constructing illumination in the plane of the aperture stop. For example, as illustrated in FIG. 3 , the illumination passageway 108 may include a lens 110a to focus the illumination beam 104 from the illumination source 102 in the plane of the aperture stop. . Additionally, illumination passageway 108 may include optical components 112 (eg, polarizers, etc.) to further condition illumination beam 104. As another example, the lighting passage 108 may include a lens 110b to relay the plane of the aperture stop. For example, lens 110b may relay the rear focal plane of objective lens 114 such that aperture stop 302 may be adjusted to provide telecentric illumination of sample 106.

In another embodiment, imaging device 100 includes one or more field apertures. In a general sense, the field of view aperture may limit the spatial extent of light in the plane conjugate to sample 106. For example, as illustrated in FIG. 3 , field of view aperture 306 in illumination path 108 may provide a layer-specific spatial extent of illumination for sample 106 . As another example, the aperture stop in the collection passageway 120 may provide layer-specific limits on the spatial extent of radiation emitted from the sample 106 used to generate the image and thus limit the image size. You can also provide it.

In other embodiments, the layer-specific imaging configuration includes an opening diameter of the field stop in the illumination passageway 108 and/or the collection passageway 120. Accordingly, imaging device 100 may include a field of view stop with an adjustable opening diameter (e.g., coupled to controller 126) for creation of layer-specific imaging configurations. Herein, adjusting the opening diameter of the field stop may limit and/or define the portion of the sample being imaged, which may facilitate high quality imaging by reducing unwanted and/or unnecessary light. It is recognized. For example, the opening diameter of the field stop may be adjusted to illuminate and/or detect only radiation from a selected radius containing features of interest on a given sample layer. In this regard, features outside this selected radius may not introduce noise into the image of features within the selected radius, which may facilitate images with high contrast, brightness, etc.

Herein, the exact location of the plane conjugate relative to the sample 106 is determined by the wavelength (e.g., of the radiation emitted from the sample 106) due to any number of factors such as, but not limited to, chromatic aberration. It is also recognized that it may vary based on the wavelength of the illumination spectrum). Accordingly, the layer-specific imaging configuration provides precise control of the field of view apertures in the illumination passageway 108 and/or collection passageway 120 to adjust the spatial extent of light in the plane conjugate to the sample 106 within selected tolerances. May also include location. For example, imaging device 100 may translate (e.g., coupled to controller 126) to position an aperture as a field stop within illumination passageway 108 and/or collection passageway 120. It may also contain stages.

In another embodiment, the layer-specific imaging configuration includes the position of the sample stage 116 that holds the sample 106. Accordingly, the layer-specific imaging configuration may include the location of the sample 106 within the focal volume of the objective lens 114. In this regard, the focusing conditions of the illumination beam 104 on the surface of the sample 106 or inside the sample 106 may be tailored for each layer of interest.

In other embodiments, the layer-specific imaging configuration includes one or more imaging parameters of detector 118. For example, layer-specific imaging configurations may, but need not, include selected settings of gain, integration time, or the like. Therefore, in order to provide images with image quality metrics (e.g., brightness, contrast, noise level, positional accuracy of features within the image, etc.) within selected tolerances, images of the different layers of interest must be tailored. It can also be captured using detector settings.

FIG. 4 is a flow diagram illustrating steps performed in a method 400 for image-based metrology with layer-specific imaging configurations, according to one or more embodiments of the present disclosure. The Applicant notes that the embodiments and implementation techniques previously described herein in the context of imaging device 100 should be interpreted to extend to method 400 . However, it is also noted that method 400 is not limited to the architecture of imaging device 100.

In one embodiment, method 400 includes a layer-specific imaging configuration of an imaging device (e.g., controller 126) to image metrology target elements on two or more sample layers of a sample within selected image quality tolerances. ), or etc.) and determining step 402. The layer-specific imaging configuration may include, but is not limited to, any combination of the illumination spectrum incident on the sample, the detection spectrum of the incident radiation, and the location of the aperture stop and/or field stop within the imaging device. No.

Image quality metrics may include, but are not limited to, image brightness, image contrast, image noise, or the like. In this regard, an illumination spectrum may be tailored for each sample layer to provide an image of a feature (e.g., a metrology target element) within a selected tolerance. In this regard, the selected tolerance can be defined as the desired pixel intensity for one or more pixels in the image, the desired average pixel intensity, the desired difference between the maximum and minimum pixel intensities of the image, random fluctuations in pixel intensity (e.g. may include a desired amount of noise), or the like.

For example, there may be instances where imaging configurations may affect image quality metrics such that the accuracy and/or repeatability of metrology measurements based on the generated images may vary. As another example, the imaging configuration affects the sensitivity of metrology measurements (e.g., overlay measurements, feature size measurements, etc.) based on the generated images to system defects due to misalignment, aberrations, etc. There may be cases where it may cause harm. Accordingly, providing layer-specific imaging configurations may facilitate the creation of images with image quality within selected tolerances and may further facilitate accurate, repeatable, and robust metrology measurements.

A layer-specific imaging configuration may include any combination of parameters of the imaging device. For example, the layer-specific imaging configuration may include the spectrum of illumination incident on the sample to produce the image. Features on each layer (eg, metrology target elements) may be imaged using a tailored illumination spectrum suitable to provide images with image quality metrics within selected tolerances. Accordingly, the illumination spectrum may, but need not be, adjusted for each layer of interest based on the properties of the surrounding layer (e.g., absorption, refractive index, thickness, or the like) of the surrounding layer.

As another example, a layer-specific imaging configuration may include a filtered spectrum of radiation emitted from the sample that is used to generate an image (e.g., a detection spectrum). In this regard, the sample layer may be illuminated with a fixed illumination spectrum, and the layer of interest may be imaged using the layer's own detection spectrum by filtering out radiation emitted from the sample prior to the detector.

As another example, the layer-specific imaging configuration may include the opening diameter and/or the location of the aperture stop. In this regard, the layer-specific imaging configuration may include the angular range of illumination incident on the sample and/or the angular range of radiation emitted from the sample used to generate an image of the sample layer. In one instance, the aperture stop is relative to the rear focal plane of a collection lens (e.g., objective lens 114) in an illumination arm (e.g., illumination path 108) of the imaging system. It may be configured to provide telecentric illumination when positioned in the plane conjugate. In another example, the aperture stop facilitates telecentric imaging of the sample when positioned in a plane conjugate to the rear focal plane of the collection lens in a collection arm of the imaging system (e.g., collection passageway 120). It may be configured to provide.

As another example, the layer-specific imaging configuration may include the opening diameter and/or the location of the field stop. Accordingly, the layer-specific imaging configuration may include the spatial extent of illumination for the image and/or the spatial extent of radiation emitted from the sample to be directed to the detector to produce the image. In this regard, layer-specific imaging configurations may include specific portions of the sample to reduce unwanted and/or unnecessary light associated with portions of the sample that are not of interest for a given sample layer image.

As another example, the layer-specific imaging configuration may include the position of the sample within the focal volume of the imaging system (e.g., as controlled by a sample stage). For example, the focal position of the sample may be adjusted to compensate for differences in the optical path between different sample layers, to compensate for chromatic aberration, etc.

As another example, a layer-specific imaging configuration may include one or more detector settings associated with image generation. For example, layer-specific imaging configurations may, but need not, include selected values of detector gain, integration time, or the like, tailored for each sample layer.

The layer-specific imaging configuration for each sample layer of interest determined in step 402 may be any known in the art suitable to provide an image of the sample layer of interest with image quality metrics within specified tolerances. It can also be configured by method. In one embodiment, a layer-specific imaging configuration is performed over a series of experiments in which potential imaging configuration parameters (e.g., illumination spectrum, detection spectrum, aperture configuration, focal position of the sample, detector settings, etc.) are varied. It is decided through In this regard, an image of the sample layer of interest (eg, an image of a feature of a metrology target on the sample layer of interest) may be generated using various candidate imaging configuration parameters. The image quality metrics for the sample layer of interest may then be compared for various combinations of imaging configuration parameters, and the imaging configuration that provides the desired set of image quality metrics may be selected for each sample layer of interest. It may be possible.

In another embodiment, the layer-specific imaging configuration includes simulating an image of a sample layer of interest (e.g., an image of a feature of a metrology target on a sample layer of interest) and an image for each sample layer of interest. Selection may be made by selecting an imaging configuration that provides a desired set of quality metrics.

Additionally, step 402 involves simulating one or more metrology measurements based on images of the sample layer (e.g., generated through measurements and/or by additional simulations) based on layer-specific image configurations. It may also be included.

Metrology measurements related to metrology target elements on a layer of the sample may include, but are not limited to, overlay measurements, critical dimension (CD) measurements, sidewall angles, and film thickness. Additionally, one or more aspects of the metrology target element may represent process-related parameters (eg, focus, dose, and the like). The target may include some region of interest that is periodic in nature, such as a grid of memory die, for example. A metrology target may further have various spatial characteristics and typically consists of one or more cells that may contain features in one or more layers, which may have been printed in one or more lithographically separate exposures. A target or cell may have various symmetries, such as two-fold or four-fold rotational symmetry or reflection symmetry. An example of such a metrology structure is described in U.S. Pat. No. 6,985,618, which is incorporated herein by reference in its entirety. Different cells or combinations of cells may belong to separate layers or exposure steps. Individual cells may contain separate aperiodic features or alternatively they may be constructed from one-, two- or three-dimensional periodic structures or a combination of aperiodic and periodic structures. The periodic structures may be unsegmented or they may be constructed from finely segmented features that may be at or close to the minimal design rules of the lithography process used to print them.

The simulation at step 402 may involve multiple algorithms. For example, but not limited to, the optical interaction of illumination beam 104 with a metrology target on sample 106 may be modeled using an electro-magnetic (EM) solver. . In addition, EM solvers include rigorous coupled-wave analysis (RCWA), finite element method analysis, method of moments analysis, surface integral technique, and volumetric analysis. Any method known in the art may be utilized, including but not limited to volume integral techniques, or finite-difference time-domain analysis. Additionally, the collected data can be used in libraries, fast-reduced-order models, regression, machine learning algorithms such as neural networks, support-vector machines (SVMs), and dimensionality-reduction algorithms. ) (e.g., principal component analysis (PCA), independent component analysis (ICA), local-linear embedding (LLE), and etc.), sparse representation of the data representation of data) (e.g., Fourier or wavelet transform, Kalman filter, algorithms that facilitate matching from the same or different tool types, and the like), but these The data may also be analyzed using, but not limited to, data fitting and optimization techniques. For example, data collection and/or fitting may, but need not be, performed by the Signal Response Metrology (SRM) software product provided by KLA-TENCOR. In another embodiment, raw data generated by a metrology tool is analyzed by algorithms that do not involve modeling, optimization, and/or fitting (eg, topological characterization, or the like).

Herein, the computational algorithms performed by the controller may be tailored to the metrology application through the use of parallelization, distributed computation, load-balancing, multi-service support, design and implementation of computational hardware, or dynamic load optimization. Note that this may be possible, but does not necessarily need to be tailored. Additionally, various implementations of the algorithm may be implemented by one or more programmable modules, either by a controller (e.g., through firmware, software, or a Field Programmable Gate Array (FPGA), and the like), or associated with a metrology tool. It may, but does not necessarily need to be done by optical elements. The use of process modeling is generally described in U.S. Patent Publication No. 2014/0172394, published June 19, 2014, which is incorporated herein by reference in its entirety.

In another embodiment, method 400 includes receiving 404 from an imaging device one or more images of metrology target elements on two or more sample layers generated using a layer-specific imaging configuration. For example, an imaging system may generate an image of a sample layer of interest using a layer-specific imaging configuration.

In another embodiment, method 400 includes providing 406 metrology measurements based on one or more images of metrology target elements on two or more sample layers. Step 406 may include, but is not limited to, overlay measurements related to the relative positions of features in different sample layers, or measurements of one or more aspects (e.g., size, orientation, etc.) of features within each layer. It may include, but is not limited to, providing any type of metrology measurement known in the art based on images of two or more sample layers.

The subject matter described herein, at times, illustrates different other components that are included within or connected to other components. It should be understood that such depicted architectures are merely illustrative, and that in practice, many other architectures may be implemented that achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “related” such that the desired functionality is achieved. Therefore, any two components combined herein to achieve particular functionality, regardless of architecture or intermediate components, may be viewed as “related” to each other such that the desired functionality is achieved. Likewise, any two components so related may also be viewed as being "connected" or "coupled" to each other to achieve the desired functionality, and any two components that may be so related may also be viewed as being "connected" or "coupled" to each other to achieve the desired functionality. can be viewed as being “coupled” with each other to achieve the desired functionality. Specific examples of coupleable include: physically interactable and/or physically interactable and/or wirelessly interactable and/or wirelessly interactable and/or logically interactable and/or It includes, but is not limited to, logically interacting components.

It is believed that many of the present disclosure and its attendant advantages will be understood by the foregoing description, including the form, configuration, and arrangement of components, without departing from the disclosed subject matter or sacrificing the entirety of the important advantages of the disclosed subject matter. It will be clear that various changes may be made in . The described forms are for illustrative purposes only, and it is the intent of the following claims to cover and encompass such modifications. Moreover, it is to be understood that the present invention is defined by the appended claims.

Claims (91)

In a metrology system,
imaging device—the imaging device:
spectrally-tunable illumination device; and
generating an image of the sample based on radiation emitted from the sample, the sample comprising metrology target elements on two or more sample layers, in response to illumination from the spectrally tunable illumination device. detector
Includes -; and
a controller communicatively coupled to the imaging device, the controller comprising one or more processors configured to execute program instructions that cause the one or more processors to:
A layer-specific imaging configuration of the imaging device for imaging metrology target elements on the two or more sample layers within selected image quality tolerances—each layer-specific imaging configuration including the lighting spectrum from a tunable lighting device;
receive from the imaging device one or more images of metrology target elements on the two or more sample layers generated using said layer-specific imaging configuration; and
A metrology system configured to provide metrology measurements based on one or more images of metrology target elements on the two or more sample layers. According to paragraph 1,
and wherein the layer-specific imaging configuration further includes image acquisition parameters of the detector. According to paragraph 2,
The metrology system of claim 1, wherein the image acquisition parameters of the detector include at least one of gain or integration time. According to paragraph 1,
The imaging device includes an aperture stop with an adjustable position, wherein the layer-specific imaging configuration provides telecentric illumination of the sample within a selected telecentricity tolerance. ), further comprising the position of the aperture stop to provide. According to paragraph 1,
The imaging device includes an aperture stop having an adjustable position, wherein the layer-specific imaging configuration further adjusts the position of the aperture stop to provide telecentric imaging of the sample within a selected telecentricity tolerance. Including, measurement system. According to paragraph 1,
The metrology system of claim 1, wherein the imaging device includes a stage for positioning the sample at an adjustable focal position of the imaging device, and the layer-specific imaging configuration further comprises a focal position of the sample. According to paragraph 1,
The spectrally tunable illumination device sequentially provides two or more illumination spectra associated with layer-specific imaging configurations of the imaging device, wherein one or more images of metrology target elements on the two or more sample layers are A metrology system comprising distinct images for at least two sample layers, wherein the detector sequentially generates distinct images for at least two sample layers based on the at least two illumination spectra. According to paragraph 1,
The spectrally tunable illumination device may have two or more spatially separated illumination spectra associated with layer-specific imaging configurations of the imaging device to provide distinct illumination spectra for metrology target elements on the two or more sample layers. and simultaneously providing, wherein the one or more images of the metrology target element on the two or more sample layers generated by the detector comprise a single image. According to paragraph 1,
The spectrally tunable lighting device includes:
Broadband lighting source; and
A metrology system comprising one or more spectral filters to modify the spectrum of the broadband illumination source. According to clause 9,
The one or more spectral filters include:
A measurement system comprising at least one of a short-pass filter, a long-pass filter, a bandpass filter, or a notch filter. According to clause 9,
The one or more spectral filters include:
A metrology system comprising one or more spectral filters with fixed spectral filtering characteristics. According to clause 11,
The spectrally tunable lighting device includes:
and at least one filter insertion device for selectively inserting one or more spectral filters with fixed spectral characteristics ahead of the sample into the path of illumination from the broadband illumination source. According to clause 12,
The filter insertion device:
A metrology system comprising at least one of a filter wheel, a linear translation device, or a flipper device. According to clause 9,
The one or more spectral filters include:
A metrology system comprising one or more spectral filters having tunable spectral filtering characteristics. According to clause 14,
One or more spectral filters having the tunable spectral filtering characteristics:
and one or more angularly-tunable spectral filters having tunable spectral filtering characteristics based on the angle of incidence of illumination from the broadband illumination source, the spectrally tunable lighting device comprising: The metrology system further comprising a filter tuning device for adjusting the angle of incidence of illumination from the broadband illumination source to one or more angularly tunable spectral filters. According to clause 14,
One or more spectral filters having the tunable spectral filtering characteristics:
A metrology system comprising a tunable double monochromator. According to clause 9,
The broadband light source is:
A metrology system comprising a supercontinuum laser source. According to clause 9,
The broadband light source is:
A metrology system comprising at least one of a laser-pumped plasma illumination source or a lamp source. According to paragraph 1,
The spectrally tunable lighting device includes:
Two or more narrowband lighting sources; and
A metrology system comprising a selection device for selecting illumination from at least one of the two or more narrowband illumination sources to image the sample. According to clause 19,
Among the two or more narrowband lighting sources, the narrowband lighting source is:
A metrology system comprising at least one of a laser source or a spectrally-filtered broadband illumination source. According to paragraph 1,
The image quality tolerances selected above are:
A metrology system comprising at least one of contrast, resolution, brightness, or noise tolerance. According to paragraph 1,
The detector:
A metrology system comprising at least one of a charge coupled device detector or a complementary metal oxide semiconductor detector. According to paragraph 1,
The metrology measurements are:
A metrology system comprising overlay measurements between the two or more sample layers. According to paragraph 1,
The metrology measurements are:
and critical dimensions of metrology target elements on the two or more sample layers. According to paragraph 1,
Determining the layer-specific imaging configuration of the imaging device:
generating, using the imaging device, an image of a metrology target element on each of the two or more sample layers using various imaging conditions; and
For each sample layer of the two or more sample layers, selecting a layer-specific imaging configuration from various imaging configurations that provides an image that meets the selected image quality tolerance. According to paragraph 1,
Determining the layer-specific imaging configuration of the imaging device:
simulating an image of a metrology target element on each of the two or more sample layers using various imaging configurations; and
For each sample layer of the two or more sample layers, selecting a layer-specific imaging configuration from various imaging configurations that provides an image that meets the selected image quality tolerance. In a measurement system,
Imaging device—The imaging device:
Broadband lighting source;
a spectrally tunable filter to spectrally filter radiation emitted from the sample in response to illumination from the broadband illumination source; and
A detector for generating an image of the sample, the sample comprising two or more sample layers, based on radiation emitted from the sample and filtered by the spectrally tunable filter.
Includes -; and
a controller communicatively coupled to the imaging device, the controller comprising one or more processors configured to execute program instructions that cause the one or more processors to:
Layer-specific imaging configurations of the imaging device for imaging metrology target elements on the two or more sample layers within selected image quality tolerances, each layer-specific imaging configuration being filtered by the spectrally tunable filter. to determine - including the spectrum of radiation from the sample;
receive from the detector one or more images of metrology target elements on the two or more sample layers generated using said layer-specific imaging configuration; and
A metrology system configured to provide metrology measurements based on one or more images of metrology target elements on the two or more sample layers. According to clause 27,
and wherein the layer-specific imaging configuration further includes image acquisition parameters of the detector. According to clause 28,
The metrology system of claim 1, wherein the image acquisition parameters of the detector include at least one of gain or integration time. According to clause 27,
The imaging device includes an aperture stop having an adjustable position, wherein the layer-specific imaging configuration further adjusts the position of the aperture stop to provide telecentric illumination of the sample within a selected telecentricity tolerance. Including, measurement system. According to clause 27,
The imaging device includes an aperture stop having an adjustable position, wherein the layer-specific imaging configuration further adjusts the position of the aperture stop to provide telecentric imaging of the sample within a selected telecentricity tolerance. Including, measurement system. According to clause 27,
The metrology system of claim 1, wherein the imaging device includes a stage for positioning the sample at an adjustable focal position of the imaging device, and the layer-specific imaging configuration further comprises a focal position of the sample. According to clause 27,
The spectrally tunable filter sequentially provides two or more filtered spectra associated with a layer-specific imaging configuration of the imaging device, wherein one or more images of a metrology target element on the two or more sample layers are selected from the two or more sample layers. A metrology system comprising separate images for at least two sample layers, wherein the detector sequentially generates separate images for at least two sample layers based on the at least two filtered spectra. According to clause 27,
The spectrally tunable filter selects two or more spatially separated illumination spectra associated with layer-specific imaging configurations of the imaging device to provide distinct illumination spectra for metrology target elements on the two or more sample layers. providing simultaneously, wherein one or more images of a metrology target element on the two or more sample layers generated by the detector comprise a single image. According to clause 27,
The spectrally tunable filter:
A measurement system comprising at least one of a short-wavelength pass filter, a long-wavelength pass filter, a band-pass filter, or a notch filter. According to clause 27,
The spectrally tunable filter:
A metrology system comprising one or more spectral filters with fixed spectral filtering characteristics. According to clause 36,
The spectrally tunable filter:
and at least one filter insertion device for selectively inserting one or more spectral filters with fixed spectral characteristics ahead of the detector into the path of radiation emitted from the sample. According to clause 37,
The filter insertion device:
A metrology system comprising at least one of a filter wheel, a linear translation device, or a flipper device. According to clause 27,
The spectrally tunable filter:
A metrology system comprising one or more spectral filters having tunable spectral filtering characteristics. According to clause 39,
One or more spectral filters having the tunable spectral filtering characteristics:
one or more angularly tunable spectral filters having tunable spectral filtering characteristics based on the angle of incidence of illumination from the broadband illumination source, the imaging device comprising: A metrology system further comprising a filter tuning device for adjusting the angle of incidence of illumination from a broadband illumination source. According to clause 27,
The broadband light source is:
Metrology system, including a supercontinuum laser source. According to clause 27,
The broadband light source is:
A metrology system comprising at least one of a laser pumped plasma illumination source or a lamp source. According to clause 27,
The image quality tolerances selected above are:
A metrology system comprising at least one of contrast, resolution, brightness, or noise tolerance. According to clause 27,
The detector:
A metrology system comprising at least one of a charge coupled device detector or a complementary metal oxide semiconductor detector. According to clause 27,
The metrology measurements are:
A metrology system comprising overlay measurements between the two or more sample layers. According to clause 27,
The metrology measurements are:
and critical dimensions of metrology target elements on the two or more sample layers. According to clause 27,
Determining the layer-specific imaging configuration of the imaging device:
generating, using the imaging device, an image of a metrology target element on each of the two or more sample layers using various imaging conditions; and
For each sample layer of the two or more sample layers, selecting a layer-specific imaging configuration from various imaging configurations that provides an image that meets the selected image quality tolerance. According to clause 27,
Determining the layer-specific imaging configuration of the imaging device:
simulating an image of a metrology target element on each of the two or more sample layers using various imaging configurations; and
For each sample layer of the two or more sample layers, selecting a layer-specific imaging configuration from various imaging configurations that provides an image that meets the selected image quality tolerance. In the method,
Layer-specific imaging configurations of an imaging device, each layer-specific imaging configuration comprising an imaging spectrum, using one or more processors, to image metrology target elements on two or more sample layers of a sample within selected image quality tolerances. A step of deciding;
Receiving from the imaging device one or more images of metrology target elements on the two or more sample layers generated using said layer-specific imaging configuration; and
A method comprising providing metrology measurements based on one or more images of metrology target elements on the two or more sample layers. According to clause 49,
The method of claim 1, wherein the imaging spectrum of the layer-specific imaging configuration comprises a spectrum of illumination incident on the sample. According to clause 49,
The method of claim 1, wherein the imaging spectrum of the layer-specific imaging configuration comprises a spectrum of radiation incident on a detector of the imaging device to produce one or more images of metrology target elements on the two or more sample layers. According to clause 51,
The method of claim 1, wherein the layer-specific imaging configuration further comprises image acquisition parameters of the detector. According to clause 52,
The method of claim 1, wherein the image acquisition parameters of the detector include at least one of gain or integration time. According to clause 49,
The imaging device includes an aperture stop having an adjustable position, wherein the layer-specific imaging configuration further adjusts the position of the aperture stop to provide telecentric illumination of the sample within a selected telecentricity tolerance. Including, method. According to clause 49,
The method of claim 1, wherein the imaging device includes a stage for positioning the sample at an adjustable focal position of the imaging device, and the layer-specific imaging configuration further comprises a focal position of the sample. According to clause 49,
Determining the layer-specific imaging configuration of the imaging device includes:
generating, using the imaging device, an image of a metrology target element on each sample layer of the two or more sample layers using various imaging conditions; and
For each sample layer of the two or more sample layers, selecting a layer-specific imaging configuration from a variety of imaging configurations that provides an image that meets the selected image quality tolerance. According to clause 49,
Determining the layer-specific imaging configuration of the imaging device includes:
simulating an image of a metrology target element on each of the two or more sample layers using various imaging configurations; and
For each sample layer of the two or more sample layers, selecting a layer-specific imaging configuration from a variety of imaging configurations that provides an image that meets the selected image quality tolerance. In a measurement system,
an imaging subsystem comprising a detector configured to image a sample, the sample comprising metrology target elements on two or more sample layers, based on illumination from one or more lenses and an illumination source; and
a controller communicatively coupled to the imaging subsystem, the controller comprising one or more processors configured to execute program instructions that cause the one or more processors to:
Layer-specific imaging configurations of the imaging subsystem for imaging metrology target elements on the two or more sample layers within selected image quality tolerances, each layer-specific imaging configuration being a selected configuration of one or more components of the imaging subsystem Including - to determine;
receive from the imaging subsystem one or more images of metrology target elements on the two or more sample layers generated using said layer-specific imaging configuration; and
A metrology system configured to provide metrology measurements based on one or more images of metrology target elements on the two or more sample layers. According to clause 58,
and wherein the layer-specific imaging configuration further includes image acquisition parameters of the detector. According to clause 59,
The metrology system of claim 1, wherein the image acquisition parameters of the detector include at least one of gain or integration time. According to clause 58,
The imaging subsystem includes an aperture stop having an adjustable position, wherein the layer-specific imaging configuration adjusts the position of the aperture stop to provide telecentric illumination of the sample within a selected telecentricity tolerance. Further including, a measurement system. According to clause 58,
The imaging subsystem includes an aperture stop having an adjustable position, wherein the layer-specific imaging configuration adjusts the position of the aperture stop to provide telecentric imaging of the sample within a selected telecentricity tolerance. Further including, a measurement system. According to clause 58,
The metrology system of claim 1, wherein the imaging subsystem includes a stage for positioning the sample at an adjustable focus position of the imaging subsystem, and the layer-specific imaging configuration further includes a focus position of the sample. According to clause 58,
The metrology system of claim 1, wherein the imaging subsystem includes a polarizer to adjust the polarization of illumination from the illumination source, and the layer-specific imaging configuration further includes polarization of illumination on the sample. According to clause 58,
The imaging subsystem sequentially provides two or more illumination spectra associated with a layer-specific imaging configuration of the imaging subsystem, wherein one or more images of a metrology target element on the two or more sample layers are and wherein the detector sequentially generates distinct images for the two or more sample layers based on the two or more illumination spectra. According to clause 58,
The imaging subsystem simultaneously provides two or more spatially separated illumination spectra associated with unique imaging configurations of the layers, wherein one or more images of metrology target elements on the two or more sample layers produced by the detector are single. A measurement system containing images of According to clause 58,
The imaging subsystem:
Broadband lighting source; and
A metrology system comprising one or more spectral filters to modify the spectrum of the broadband illumination source. Paragraph 67:
The broadband light source is:
Metrology system, including a supercontinuum laser source. Paragraph 67:
The broadband light source is:
A metrology system comprising at least one of a laser pumped plasma illumination source or a lamp source. According to clause 58,
The imaging subsystem:
Two or more narrowband lighting sources; and
The metrology system further comprising at least one of a beam combiner or one or more shutters for selecting illumination from at least one of the two or more narrowband illumination sources to image the sample. According to clause 70,
Among the two or more narrowband lighting sources, the narrowband lighting source is:
A metrology system comprising at least one of a laser source or a spectrally filtered broadband illumination source. According to clause 58,
The image quality tolerances selected above are:
A metrology system comprising at least one of contrast, resolution, brightness, or noise tolerance. According to clause 58,
The detector:
A metrology system comprising at least one of a charge coupled device detector or a complementary metal oxide semiconductor detector. According to clause 58,
The metrology measurements are:
A metrology system comprising overlay measurements between the two or more sample layers. According to clause 58,
The metrology measurements are:
and a critical dimension of at least one metrology target element on at least one sample layer of the two or more sample layers. According to clause 58,
Determining the layer-specific imaging configuration of the imaging subsystem:
generating, using the imaging subsystem, an image of a metrology target element on each of the two or more sample layers using various imaging conditions; and
For each sample layer of the two or more sample layers, selecting a layer-specific imaging configuration from various imaging configurations that provides an image that meets the selected image quality tolerance. According to clause 58,
Determining the layer-specific imaging configuration of the imaging subsystem:
simulating an image of a metrology target element on each of the two or more sample layers using various imaging configurations; and
For each sample layer of the two or more sample layers, selecting a layer-specific imaging configuration from various imaging configurations that provides an image that meets the selected image quality tolerance. In the imaging system,
an illumination source configured to generate an illumination beam;
a sample stage including one or more translation stages for selectively adjusting the position of a sample, the sample comprising metrology target elements on two or more sample layers;
one or more illumination optics configured to direct the illumination beam to the sample, the one or more illumination optics comprising a polarizer for selectively adjusting polarization of the illumination beam;
one or more collection optics configured to collect radiation emitted from the sample in response to the illumination beam;
a detector configured to generate an image of the sample based on radiation emitted from the sample collected by the one or more collection optics; and
a controller communicatively coupled to at least one of the illumination source, any of the one or more illumination optics, any of the one or more collection optics, or the detector, the controller executing program instructions; One or more processors configured to: wherein the program instructions cause the one or more processors to:
Layer-specific imaging configuration for the two or more sample layers—each layer-specific imaging configuration may be configured to determine the spectrum of the illumination source, the polarization of the illumination beam, or the polarization of the illumination beam to image a particular sample layer of the two or more sample layers. receive the location of the sample, including at least one selected configuration;
generate images for the two or more sample layers using said layer-specific imaging configuration; and
An imaging system configured to generate metrology measurements based on the two or more images. According to clause 78,
and wherein the layer-specific imaging configuration further comprises image acquisition parameters of the detector. According to clause 79,
An imaging system, wherein the image acquisition parameters of the detector include at least one of gain or integration time. According to clause 78,
The one or more illumination optics include an aperture stop having an adjustable position, wherein the layer-specific imaging configuration adjusts the position of the aperture stop to provide telecentric illumination of the sample within a selected telecentricity tolerance. Further comprising: an imaging system. According to clause 78,
The one or more collection optics include an aperture stop having an adjustable position, wherein the layer-specific imaging configuration modifies the position of the aperture stop to provide telecentric imaging of the sample within a selected telecentricity tolerance. Further comprising: an imaging system. According to clause 78,
The imaging system of claim 1, wherein the one or more collection optics comprise a collection polarizer, and the layer-specific imaging configuration further comprises polarization of emitted radiation from the sample incident on the detector. According to clause 78,
The layer-specific imaging configuration includes a spectrum of the illumination source, the illumination source sequentially provides two or more illumination spectra associated with the layer-specific imaging configuration, and the detector provides a spectrum of the two or more illumination spectra. An imaging system that sequentially generates separate images for the two or more sample layers based on the two or more sample layers. According to clause 78,
The illumination source simultaneously provides two or more spatially separated illumination spectra associated with a unique imaging configuration of the layer, and one or more images of metrology target elements on the two or more sample layers produced by the detector are a single image. An imaging system, comprising an image. According to clause 78,
The lighting source is:
Broadband lighting source; and
An imaging system comprising one or more spectral filters to modify the spectrum of the broadband illumination source. According to clause 78,
The imaging system:
Two or more narrowband lighting sources; and
The imaging system further comprising at least one of a beam combiner or one or more shutters to select illumination from at least one of the two or more narrowband illumination sources to image the sample. According to clause 78,
The metrology measurements are:
An imaging system comprising overlay measurements between the two or more sample layers. According to clause 78,
The metrology measurements are:
and a critical dimension of at least one metrology target element on at least one sample layer of the two or more sample layers. In the method,
Layer-specific imaging configurations of an imaging subsystem for imaging metrology target elements on two or more sample layers of a sample within selected image quality tolerances—each layer-specific imaging configuration being a selected configuration of one or more components of the imaging subsystem Including - determining;
generating, using the imaging subsystem, one or more images of metrology target elements on the two or more sample layers using imaging configurations specific to the layers; and
A method comprising providing metrology measurements based on one or more images of metrology target elements on the two or more sample layers. According to clause 90,
Each layer's unique imaging configuration may be determined by the spectrum of the illumination source, the polarization of the illumination beam, the illumination telecentricity, the imaging telecentricity, or the position of the sample for imaging a particular sample layer of the two or more sample layers. , a method comprising at least one selected configuration.

Images